Integrated circuits are typically comprised of individual dies or chips. A plurality of such is typically fabricated on a single substrate commonly referred to as a wafer. At the conclusion of fabrication at the wafer level, the chips/dies are singulated from the substrate typically by cutting or sawing. The individual chips are then frequently packaged and attached to other chips or other electronic structures such as a printed circuit board. The packaging and/or attachment of the chip might be accomplished by a wire bonding process, a flip-chip attachment process, or some other process. Further, wafer scale integration has been proposed whereby the integrated circuit or circuits are encompassed in a single wafer that is not singulated into individual die or chips.
Regardless, integrated circuit design typically forms bonding pads at varying locations at the outermost portion of the integrated circuit. Such locations might be grouped centrally relative to the substrate within which the integrated circuit is fabricated, grouped peripherally, or a grouped in a combination of peripherally and centrally. However, it is often desirable to have the bondpads in a different pattern, in a different size, and/or at different locations atop the chip/substrate. This requirement has lead to what is known as redistribution wherein the bondpad connection points of an integrated circuit originally at one location on the chip are redistributed to other locations. The initially located bondpads are typically referred to as inner lead bondpads. Redistribution lines are fabricated to extend from the inner lead bondpads to what are referred to as outer lead bondpads where wire bonding, solder ball or other conductive connection occurs to other devices or structures. Inner lead bondpads typically have their outermost surfaces received elevationally inward as compared to those of outer lead bondpads. Further in many instances, the inner lead bondpads are received radially inward compared to the outer lead bondpads.
The redistribution lines are typically formed over an insulative passivation material, for example polyimide. The redistribution lines are subsequently globally covered by another polyimide or other insulative passivation layer. Unfortunately, the thermal expansion coefficients of the passivation layers in comparison to other materials of the underlying substrate can be quite different. This can cause undesirable lateral displacement of the outer passivation layer from the redistribution lines and/or cracking of one or more passivation layers during processing which conventionally includes heating and cooling of the substrate.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.